The present invention relates to a so-called mark-edge recording in which marks are recorded in certain areas of a recording medium so that their physical property is made different from the other areas to thereby have information associated with both ends of each of the marks.
The present invention is particularly suited to a rewritable high-density information recording method capable of recording information to be repeatedly rewritable. The present invention is also suited to a so-called phase-changing type information recording method in which the physical property of the information recorded areas is made different from the other areas by the phase change of the recorded substance that is caused by changing the temperature of the information recording medium.
A conventional rewritable information recording method is disclosed in, for example, JP-A-63-229625. This method is an optical disk recording method for recording information by modulating the intensity of light.
As shown in FIG. 6, information is recorded in a plurality of sectors 21, each of which has identification information 24 provided at its head in order to indicate the physical position of information. This identification information 24 is used as a reference to be followed by a synchronizing signal portion 22 and an information recorded portion 23 which are recorded as a record unit on the recording medium. At this time, the start position of the record unit is randomly changed in its position at each time of rewriting, thereby increasing the possible number of times of repeated rewriting. In other words, the disk material at the same place within a sector is prevented as much as possible from being deteriorated by repeated rewriting, thereby raising the possible number of times of repeated writing.
FIG. 7 illustrates the relation between the number of times of rewriting and the jitter in the case where the same recording information is repeatedly recorded. Here, the jitter is defined as the standard deviation normalized by a reproduction detection window width, the standard deviation being of the time shift between a reproduction clock and a reproduced data after the same random data is EFM-modulated, recorded repeatedly and then reproduced.
In FIG. 7, a curve 701 was obtained when the start position of the recorded portion is shifted by 2 bytes in the mark-edge recording, a curve 702 when shifted by 30 bytes in the mark-edge recording, a curve 703 when shifted by 2 bytes in the mark-position recording, a curve 704 when shifted by 100 bytes in the mark-edge recording, and a curve 705 when shifted by 30 bytes in the mark-position recording. Here, the mark-position recording is the recording system in which information is recorded in association with the center position of the mark.
From FIG. 7, it will be seen that the increase of jitter after rewriting can be suppressed more, or the possible number of times of rewriting is increased as the amount of the shift of the start position of the recorded area is increased. Here, the minimum mark distance, in the mark-position recording in which data is associated with the center position of the mark, was selected to be 0.9 xcexcm, and the minimum mark distance, in the mark-edge recording in which data is associated with both ends of the mark, was chosen to be 0.6 xcexcm. In addition, the diameter of the recording and reproducing spot was 0.9 xcexcm, and the recording medium used was a GeSbTe-based phase-change recording medium.
However, in the start-position shift system, and particularly in the mark-edge recording, the shift of the start position of the randomly recorded data must be increased to about 100 bytes in order to achieve a practical possible number of times of rewriting, as will be understood from FIG. 7, when the same information is repeatedly rewritten. Therefore, the utilization efficiency of sectors was greatly reduced. In addition, under this great positional shift, the beginning end or last end of recorded information will be superimposed upon other recorded portions. Since the recording characteristics of the beginning end or last end of recorded information are deteriorated probably due to the dissolution or flow of the recorded film, the effect of the change of the recording and production characteristics may be expanded over a wide range by repeated rewriting of these portions.
It is an object of the present invention to provide an information recording method capable of greatly increasing the possible number of times of repeated rewriting without reducing the recording efficiency in a rewritable high-density information recording method for repeatedly rewriting information so that the recorded information can be associated with both ends of a mark.
It is another object of the invention to provide an information recording apparatus capable of greatly increasing the possible number of times of repeated rewriting without reducing the recording efficiency in a rewritable high-density information recording method for repeatedly rewriting information so that the recorded information can be associated with both ends of a mark.
The present invention, in order to achieve the first object, provides the following aspects.
(1) An information recording method is provided for repeatedly recording information on a recording medium in association with both ends of each of marks that are formed to be different in their physical property from other areas, wherein each time information is recorded, the marks and the spaces between the marks are substantially randomly inverted in their positions.
Thereby, when repetitive rewriting is made, the total number of times that the marks and spaces are recorded is uniform over all the medium, and therefore the medium is physically uniformly changed by repetitive recording. Accordingly, the possible number of times of repetitive rewriting can be greatly increased. This does not reduce the information recording efficiency at all.
(2) The substantially random inversion is made at each record unit.
Here, the record unit is a unit such as a sector that is actually recorded on the recording medium. In other words, any smaller ones than these record units are never rewritten as information on the recording medium. Of course, it is possible that after the record units are reproduced, only part of the reproduced information is modified and again recorded as in the read-modify-write process so that the minimum unit to be recorded can be apparently reduced. However, even in this case, the above-given record units are actually recorded on and reproduced from the medium. If this inversion occurred within the record unit, a complicated process would be necessary at the time of signal reproduction.
Thereby, the total number of times that marks are recorded in each record unit is uniform over the record unit. Since the reproduction process is generally made for each information record unit, the change of the medium due to repetitive recording of each record unit is uniform, and thus the possible number of times of repetitive rewriting can be increased.
(3) An information recording method is provided for repeatedly recording information on a recording medium in association with both ends of each of marks that are formed to be different in their physical property from other areas, wherein a synchronizing signal formed of a plurality of marks is provided at the head of an information recorded portion, and the number of marks of the synchronizing signal is changed each time information is rewritten so that the length of the synchronizing signal can be substantially randomly changed.
Thereby, since the region in which the synchronizing signal is recorded is used as an adjustment region, the position of the information recorded portion is substantially randomly changed. Therefore, when repetitive rewriting is made, the total number of times that the marks and spaces are repeatedly recorded is uniform over all the medium in each record unit. Consequently, the recording medium is uniformly changed in the physical property by the repetitive recording with the result that the possible number of times of repetitive rewriting can be greatly increased.
(4) An information recording method is provided for repeatedly recording information on a recording medium by forming recorded marks that are different in their physical property from other areas so that the information corresponds to both ends of each of the marks, wherein a synchronizing signal having a plurality of marks and spaces is provided at the head of the information recorded portion, and each time the information is rewritten, the number of the marks or the spaces of the synchronizing signal is changed so that the length of the synchronizing signal is substantially randomly changed, and the marks and the spaces between the marks are substantially randomly reversed in their positions.
Thereby, when repetitive rewriting is made, the total number of times that the marks and spaces are repeatedly recorded is more uniform over the medium, and hence the possible number of times of repetitive rewriting can be more increased.
(5) The length of a guard portion which has dummy data and is provided at the back end of the information recorded portion is changed depending upon the length of the synchronizing signal portion. Therefore, the total length of the record unit ranging from the head of the synchronizing signal portion to the back end of the guard or dummy data portion is substantially unchanged.
Thereby, since the total length of the record unit is substantially unchanged, the change of the beginning end and last end of information does not affect the information recorded portion at the center of the information. Therefore, the possible number of times of repetitive rewriting can be suppressed from being reduced by the effect of the change of the beginning end and back end of information.
(6) Each time the information is rewritten, the information recording start position is substantially randomly changed.
Thereby, when repetitive rewriting is made, the total number of times that the marks and spaces are repeatedly recorded can be made more uniform over the medium. Therefore, the possible number of times of repetitive rewriting can be more increased.
(7) An information recording method is featured in that the change of the information recording start position is smaller than that of the length of the synchronizing signal.
Thereby, the change of the beginning end and back end of information does not affect the central portion of information, or the information recorded portion irrespective of the change of the information recording start position. Consequently, the possible number of times of repetitive rewriting can be suppressed from being reduced by the effect of the change of the beginning end and back end of information. Therefore, the possible number of times of rewriting can be greatly increased.
The present invention, in order to achieve the second object, provides the following aspects.
(8) An information recording apparatus is provided for recording information on a recording medium by a structure having at least a record/reproduce head and a recording pulse generation circuit, further including at least a random signal generation circuit, a timing generation circuit, and any one of at least a polarity inverting circuit for inverting the recording pulse polarity in accordance with a random signal generated from the random signal generation circuit, and a synchronizing signal generation circuit having a function to change the length of the synchronizing signal.
Thus, since at least one of the polarity and timing of the recording pulse can be changed during recording, the total number of times that the marks and spaces are repeatedly recorded when repetitive rewriting is made can be made uniform over the medium. Consequently, the possible number of times of repetitive rewriting on the recording medium can be increased.
Here, the recording pulse is not any one of the pulses themselves of heat, light and magnetic field to be applied to the medium at the time recording on the medium. The actual pulse to be applied to the medium is formed after being converted by a recording pulse shaping circuit or the like into a multi-pulse train or the like depending on the characteristic of the medium, and then recorded.
(9) In addition, the recording pulse is passed through a synthesizing circuit after the generation of the synchronizing signal, coded data and dummy data, and then its polarity is inverted.
Thus, the polarity can be surely inverted without dependence on the encoding circuit and system for recording.
(10) The polarity of the synchronizing signal generated from the synchronizing signal generation circuit is at least changed in accordance with the above-mentioned random signal.
Thus, since the polarity of the recording pulse can be automatically inverted without additionally providing a polarity inverting circuit, the apparatus can be fabricated at low cost.
As described above, according to the present invention, there is provided an information recording method for recording information on the medium in a form of an array of recorded marks so that the xe2x80x9c0xe2x80x9ds or xe2x80x9c1xe2x80x9ds of binary information are made associated with both ends of each of the recorded marks, and featured in that if the same information is recorded a plurality of times, an array of recorded marks recorded on the medium according to the information includes an array in which the recorded marks and the spaces between the marks are inverted in their positions. Therefore, even though the same information is repeatedly recorded on the medium, the marks are not formed at a particular location, but can be uniformly formed over the medium by an energy beam, and thus the life of the recording medium can be expanded.
Moreover, the recording medium of the invention has formed along tracks a plurality of sectors each of which has a data region in which the recording data is recorded, a synchronizing signal region provided before the data region, and a dummy data region provided after the data region, the length of the synchronizing signal region included within each sector being not constant, the length of the range from the head of the synchronizing signal region to the back end of the dummy data region being constant.
Furthermore, a preferred embodiment of the medium has formed along tracks a plurality of sectors each of which has a data region in which the recording data is recorded, first and second regions provided before and after the data region, and an identification information portion provided before the first region, the length of the first region within each sector being not constant, the length of the range from the head of the first region to the back end of the second region being constant, the distance from the head of the first region to the back end of the identification information portion being not constant.
Thus, the recording medium is deteriorated uniformly by the irradiation of energy beam, and hence high reliability can be ensured.